jpadilla PyJWT up to 2.13.x raw-JWK detector jwt/algorithms.py HMACAlgorithm.prepare_key improper authentication

Summaryinfo

A vulnerability described as critical has been identified in jpadilla PyJWT up to 2.13.x. Affected by this issue is the function HMACAlgorithm.prepare_key of the file jwt/algorithms.py of the component raw-JWK detector. The manipulation results in improper authentication. This vulnerability is reported as CVE-2026-102272. The attack can be launched remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as critical has been found in jpadilla PyJWT up to 2.13.x. Affected is the function HMACAlgorithm.prepare_key of the file jwt/algorithms.py of the component raw-JWK detector. The manipulation with an unknown input leads to a improper authentication vulnerability. CWE is classifying the issue as CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.prepare_key in jwt/algorithms.py is affected because raw-JWK detector does not normalize accepted Unicode byte-order marks before checking for JSON. This occurs when a public JWK is prefixed with a UTF-8 BOM and used in a mixed-algorithm verification path. As a result, public JWK bypasses asymmetric-key detection and becomes the HMAC secret. Consequently, an attacker who knows the public key can forge authenticated tokens. This issue is fixed in version 2.14.0.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-102272 since 09/28/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available.

Upgrading to version 2.14.0 eliminates this vulnerability.

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Productinfo

Vendor

• jpadilla

Name

• PyJWT

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9
• 2.10
• 2.11
• 2.12
• 2.13

Website

• Product: https://github.com/jpadilla/pyjwt/

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